Many properties, for instance private houses and offices, are today devised with built-in ventilation systems in order to provide a better in-door climate for the residents and employees. In many present ventilation systems the air-flow is however the same independent of the need for ventilation, that is independent of if e.g. a room is filled with people or not. These ventilation systems therefor cause unnecessary consumption of energy and raised energy costs. In order to satisfy the demands of the future of lowered energy costs the air-flow has to be reduced extensively when few or no people are present, and be able to work with high flows when many people are present. The ventilation system therefore has to be devised with valves capable of within a wide flow range, without causing disturbing noise for that reason. The flow has to be adjusted to the real need for ventilation but at the same time satisfy the hygiene limits regarding temperature, CO2 concentration, draft and a low sound level. By providing cooled air (16–17° C.) in a way that does not cause a resulting draft, in combination with controlling of the energy supply to heat radiators at the windows means that it is possible to obtain an optimal solution for the in-door climate throughout the year. This way excess heat from people, computers and incoming sunlight can be controlled without the need for cooled baffles or large amounts of air. This brings about that supply air terminals must be able to spread the cooled air in a way that does not cause a draft and does not cause the sound level to exceed given limits when the flow is reduced to a minimum of a few liters per second.
Among the ventilation systems known today there is no system capable of meeting the requirements above. In many ventilation systems the air-flow is adjusted for instance by means of a conventional damper, such as a throttle valve. When reducing the air-flow in these systems a significant pressure difference occurs over a very short distance at the edge of the plate, which gives rise to a considerable amount of turbulence, i.e. a powerful sound is generated over the edge of the plate. In order to lower the sound level in the room to an acceptable level, i.e. to approximately 30 dB(A), a silencer is therefore needed. Furthermore, a throttle damper cannot reduce the air-flow efficiently since there will be a small open gap between the plate and the housing of the damper even in a closed state. There are throttle dampers arranged with a rubber sealing but these are not advantageous to use since they demand actuators with high torque.
If a conventional supply air terminal, devised for stationary flows, is used together with a throttle damper in order to obtain ventilation adaptable to the current need using cooled air, the air-speed in the terminal would be so low at small flows that a cold air dropping effect will occur, i.e. that air pours out of the ventilation system without being spread in an adequate manner in the room. This is a problem for instance in certain conference installations were conference participants placed in the vicinity of the ventilation device experience that cold air is blown upon them, whereas participants located at a distance from the device will not experience any ventilation at all. Consequently, this is an effect of the air not being spread in an optimum way.
The need for cooling work facilities has increased enormously during recent years, which has led to the repeated braking of energy consumption records during the summer months. Even during the other parts of the year the need for cooling is considerable due to the ever increasing use of computers and other electronic equipment. The most common way of controlling the indoor temperature has been to use heat elements and cooling baffles in places with high requirements on temperature stability. Fancoil, a cooling device with a built-in fan is another solution. These solutions demand that a supply system for a circulating cooling medium is arranged in the facility, which is both energy demanding and brings about a high investment cost. Another way of solving the cooling need is to supply cooled air. This puts a high demand on the mixing in of the cooled air into the present warmer air in the room, so that a cold draft does not result. Furthermore, the flow of cool air has to be varied in relation to the existing need, so that the room does not get too cold. A supply air terminal for this purpose hence has to be able to increase and reduce the flow without causing cool air to simply drop down, as previously explained. Because of these difficulties in the prior art to cope with these demands, it has only been possible to supply input air which is a few degrees cooler than the ambient room temperature. Because of this, large amounts of air need to be supplied in order to obtain a sufficient cooling effect, which in turn means that the ducts or conduits of the entire ventilation system has to be dimensioned thereafter. Furthermore, it has not been possible to reduce the flow to a desired extent of only a few liters per second due to the resulting dropping cold air and damping noise.
One example of the prior art technique is shown in FIG. 1. The valve in this device comprises a tube 1 with a conduit 2 for input of air, preferably arranged with an output orifice 3 at a ceiling 4. A flow reducing device 5 is further devised with a surface 6 facing a orifice 3 of the tube. The supply flow of air through the tube 1 mainly occurs in the directions of arrows a and b. The air-flow is adjusted by raising or lowering the flow reducing device 5, which is illustrated by the bi-directional arrow in the figure, for opening of the gap between the surface 6 and the orifice 3. A dashed line in the figure illustrates that the flow reducing device 5 in some way is fixed to the tube 1 or to the ceiling 4, and is adjustable in different height positions. Actuators for adjusting the air-flow can be applied with some form of driver means, wherein the position preferably is adjusted by means of pneumatics under control of mechanical temperature sensors. In a simpler embodiment the actuator can be manually adjustable, for instance constituted by a screw in an oblong hole.
A disadvantage with the solution according to FIG. 1 is that, as with a throttle damper, or an iris damper for that matter, reduction is achieved in one point, or rather at the verge of the orifice 3. A large reduction with very small air-flows, i.e. when the plate is upraised, therefore brings about an increased sound level because of the turbulence which is formed alongside the edges of the orifice 3 during the powerfull pressure change. In order to avoid this the distance between the tube 1 and the flow reducing device 5 is usually limited by use of spacers, wherein the air-flow cannot be completely reduced. Hence, the air-flow cannot be completely adjusted based on the need for ventilation, wherein it is hard to obtain the desired saving effects.
Another disadvantage with the device according to FIG. 1 is that a flow regulation is carried out with a pressure from a supply air acting towards the adjustable flow reducing device 5. When reducing the flow, i.e. when the flow reducing device 5 is brought towards the orifice 3, the flow reducing device will hence work towards the air pressure present in the air conduit in the tube 1, caused by both static and dynamic pressure. This means that a certain force will be needed for reducing the flow, and that for dynamic adjustment an engine is needed which engine is devised such that it is capable of exercising the necessary work. However, it is desirable that said engine is as quite as possible, since it is placed inside an office facility or the like, and is adjusted dynamically dependent on certain given parameters. At the same time, one realises that the higher work the engine has to exercise, the more sound is generated.
SE 442669 discloses a supply air terminal wherein a cone-shaped flow reducing device is arranged to be brought closer or farther away from an inlet tube opening for the purpose of regulating the flow. The disclosed solution uses the same principles as the prior art according to FIG. 1, and hence suffers from the same drawbacks.
DE 2105077 relates to a self-regulating valve for constant flows, adapted to compensate for variations in the input air pressure. A spring mechanism is used such that in case of a pressure drop in the input air the damper opening is regulated in order to help maintain a steady flow.
SE 516616 discloses an air distributor, devised to be manually operated to direct the divergence of the output beam of air. A blade ring is mounted in a stationary position in relation to an outermost tube which includes a collar. In the air distributor there is a displaceable separate cylinder pipe which is used for guiding air and which can be brought into different regulation positions in relation to the stationary blade ring. The apparatus is not devised for, nor capable of, regulating the output flow, but is devised to control the divergence of the output beam by displacing the separate cylinder pipe such that a variable portion of the input air is passed through the blade ring, an a complementing portion is passed outside the separate cylinder pipe.
Another problem associated with ventilation systems of the prior art is the implementation of fire dampers. In order to prevent smoke and hot gases from spreading in the ventilation system, causing damage or potentially spreading a fire, basically every ventilation system of today is devised with some form of shut-off function in the form of fire dampers. Therefore, both a flow regulating device and a fire damper is usually located in the same duct, since no satisfying solution to combine the two has been provided. A fire damper must be capable of completely closing off the duct, which means that if a throttle valve is used it has to be provided with a rubber sealing around its damper blade. The drawbacks of such a device are many due to the friction caused. Both the rubber sealing and the actuator, which is often exercised every day in order to check its function, will become worn out prematurely, and the closing speed of the fire damper will be slow due to the dry friction.
U.S. Pat. No. 4,397,223 relates to a reciprocating actuator for a valve in the form of an air diffuser. The actuator is devised to react to fire or high heat, and to close the valve in such case. Since the spring used to close the valve in case of the aforementioned situations has to work against the air pressure in the connecting pipe, a latch mechanism has been provided to prevent the valve from opening in case the pressure exceeds the closing force of the spring.
U.S. Pat. No. 2,367,104 describes an air distributor having a damper construction with two flat cones for distributing air supplied from the device. A first cone is used as a damper for reducing the air flow by adjustment of the output opening of the device. The other cone is not passed by the output air, but merely uses the speed of the output air to suck air present in the room through the space between the two cones, in order to cause an injection of the fresh air with the present air.
The present invention relates to a valve which fulfils the requirements above and which does not display the disadvantages associated with the prior art.